Cylinder lens lapping machine



Oct. 23, 1951 A. BUTLER 2,572,443

CYLINDER LENS LAPPING MACHINE Filed Nov. 24, 1948 5 Sheets-Sheet} lNVENTOR ALBERT BUTLER AT'T'YS Oct. 23, 1951 A. BUTLER 2,572,443

CYLINDER LENS LAPPING MACHINE Filed Nov. 24. 1948 5 Sheets-Sheet 2 "warn-o9. ALBERT BUTLER Oct. 2-3, ,1951 A. BUTLER 2,572,443

I CYLINDER LENS LAPPING MACHINE I Filed Nov; 24, 1948 5 Sheets-Sheet 3 INVENTOR ALBERT BUTLER Oct. 23, 1951 t A. BUTLER 2,572,443

CYLINDER LENS LAPPING MACHINE Filed Nov. 24, 1948 5 Sheets-Sheet 4 lNVE-NTOR ALBERT BUTLER Oct. 23, 1951 BUTLER 2,572,443

CYLINDER LENS LAPPING MACHINE Filed Nov, 24, 1948 5 Sheets-Sheet 5 mvzu-row.

ALBERT BUTLER Patented Oct. 23, 1951 CYLINDER LENS LAPPING MACHINE Albert Butler, Toronto, Ontario, Canada, assignor to Percy Hermant Limited, Toronto, Ontario, Canada, a corporation of Canada Application November 24, 1948, Serial No. 61,881

1 Claim.

This invention relates to a machine forilapping cylinder lenses. In the manufacture of lenses for optical purposes it is usual to finish one surface at the factory and to leave the other surface to be prescription ground by an optician. Thi invention relates to a machine which would ordinarily be employed for finishing the factory finished side of a lens. It might, however, have other applications.

After the cutting operation a lens surface is very rough. A great deal of the roughness is taken off by an operation called fining. Further roughness is removed in a polishing operation. The remaining scratches and blemishes, however, are removed in a superfine polishing operation called lapping. This latter mentioned lapping operation is the finest of the polishing operations performed on a lens and in it the lens is caused to frictionally engage witha polishing lap having cylindrical surfaces which correspond to the cylinder surfaces of the lens.

Up to the present time the machines employed to perform this lapping operation have been cumbersome in nature and have required considerable disassembling and re-assembling when it was desired to lap lenses of different curvatures. As a consequence a great deal of the time consumed in the lapping of lenses was taken up by making adjustments to the lapping machine. Moreover the construction of these machines has been such that the moving parts required frequent replacement. I have devised a lapping machine which can be readily changed over to lap a plus or a minus lens. The construction of the machine is further such that the moving parts will not wear out in an unduly short period of use.

It is then an object of this invention to provide a cylinder lapping machine which can be readily changed over to lap lenses of different curvatures.

It is a further object of the invention to provide the cylinder lens lapping machine of the above mentioned class that is rugged during use.

It is a further object of the invention to provide a lens lapping machine capable of lapping a plurality of lenses at one time.

It is a still further object of the invention to provide a lens lapping machine which is capable of ready adjustment to suit lapping conditions required for various types of lens.

It is a still further object of this invention to provide a cylinder lens lapping machine which will lap lenses efliciently and quickly.

A lens lapping machine of the class to which this invention relates comprises a frame adapted to mount a polishing head which engages with a lens holding chuck to oscillate a lens retained therein over a lap mounted in a lap holder. The lap holder in turn is adapted to swing in an arc beneath the oscillating lens. According to the invention the lap holders are detachably mountable on shafts which are rockably mounted in the frame. The lap holder carrying shafts are arranged in pairs with their longitudinal axes in parallel spaced apart relation to each other. Only one shaft of each pair carries a lap holder at a time. The lap holders extend from the shaft to which they are connected towards the other shaft with which the first mentioned shaft forms a pair to retain a lap carried thereby in spaced apart relation to the first mentioned shaft. The spacing is designed such that the upper surface of the lap will trace out a locus which coincides with a curved surface of the lap as the shaft rocks. The polishing heads have spring means designed to urge the lens against the lap and oscillate it thereover with a polishing motion. Means are provided for rocking the polishing heads to vary the area of the lap over which the lens oscillates. The invention will be clearly understood after reference to the following detalied discussion taken in conjunction with the drawings.

In the drawings:

Figure l is a perspective view of a cylinder lens lapping machine constructed according to the invention.

Figure 2 is a plan sectional view of the machine showing the drive means for the rockably mounted lap carrying shafts.

Figure 3 is a view along the lines 33 of Figure 2 further illustrating the drive means of the rockably mounted lap carrying shafts.

Figure 3a is a detailed side view showing the means for adjusting the amount of swing of the rockably mounted lap carrying shafts.

Figure 3b is an enlarged view of a block used in the adjusting means of Figure 3a.

Figure 4 is a partial plan View of the machine broken away to show construction of the drive means for rocking the polishing heads.

Figure 5 is a sectional view showing the construction of a polishing head.

Figure 5a, is a cross sectional view along line 5a5a of Figure 5 showing the coupling of the splined telescoping shafts.

Figure 6 is a view taken from the side showing the manner in which a lap holder, designed to hold a minus lap, is carried by one of the rockable. shafts in an operative position.

Figure '7 shows a lap holder designed to retain a plus lap in an operative position.

Referring to the drawings and at first to Figure 1 in a general manner, the letter A indicates a cylinder lens polishing machine constructed according to the present invention. It comprises a case or frame 15 having four shafts rotatably mounted therein. In the view shown in Figure 1 the mounting of these shafts cannot be seen. Their free ends, however, extend from the casing I and are designed to carry lap holders II and I2 which, in turn, are designed to support polishing laps I3 and I 4 in an operative position beneath the polishing heads I9 and 2G. The lap I3 polishes a lens with a minus curve and the lap I4 polishes a lens with a plus curve. Within the casing I9 there are drive means for rocking the shafts to cause the lap holders II and I2 to swing in an arc beneath the polishing heads andZIl. As will be seen from Figure l, the lap holderl I extends downwardly from the rockable shaft by which it is carried and the lap holder I2 extends upwardly from the rockable shaft by which it is carried to an extent to cause the curved surfaces of the cylinder laps I3 and I4 respectively retained therein to trace out a locus thatsubstantially coincides with a curved surface formed thereon. It should. perhaps, be stated that the polishing laps I3 and I 4 have base and cross curve surfaces similar to the base and cross curve surfaces of lenses retained in the chucks 17 and I8, and also that the axes of the base cylindrical surfaces of the lenses substantially coincide with the axes of the base cylindrical surfaces of the laps and the axes of the cross cylindrical surfaces of the lenses sub stantially coincide with the axes of the cross cylindrical surfaces of the laps in operation. By cylindricalsurface'l mean a surface generated when a rectangle is rotated about one of the sides and by axisof a cylindrical surface, I mean the side of the rectangle about which the rectangle is rotated.

Lenses I 5 and I6, in lens chucks I! and I8,

are spring urged against laps 13 and I4 respectively by spring means within the polishing heads I9 and 29. The twin heads I9 and 23 are similar in construction and each have a rotatable shaft 12 I. (see Fig.5) with an eccentrically mounted pin 22 at its free end designed to engage in a hole bored in the lens chucks I! and I8 to cause them to oscillate the lenses with a circular polishing motion over the laps I3 and I4 as they rotate. Guide means in the form of fingers 23 extending downwardly from the axis brackets 24 on the heads 19 and 2! in parallel spaced apart relation to each other receive the aligned arms Ila of the chuck I1 therebetween to keep the principal axes of the cylindrical surfaces of the base and cross curves of the lenses I5 and I5 and laps I3 and I4 respectively in alignment with each other.

The heads I9 and 2!] are rigidly connected to each other and are pivotally mounted in the brackets 25 and 26 on the casing I I]. Drive means comprising the reciprocating drive rod 2! are provided for rocking the heads I9 and within their mounting brackets and 26 to a slight degree to vary the area of the lenses over which the polishing chucks oscillate. This will be referred to in greater detail later.

The above description will be expanded later. The purpose of setting it out in a general manner at this point is merely to give the reader a perspective view of the machine as a whole. be-

' apart guide members 23.

fore developing the various interrelated parts that combine to produce the machine as a whole.

The operation of the machine is roughly this:

Lap holders I I and I2 are mounted on the projecting free ends of the above mentioned rock-- able shafts in a manner which will be described later and appropriate laps I3 and I I are clamped: therein. Lenses I5 and I6 are' mounted in a known manner in the chucks I? and I8 and the aligned arms Ma and ill) of the lap holderare caused to pass between the parallel spaced The eccentric pin 22 engages with the chuck and the heads 19 and 28 are caused to urge the chucks against the laps.-

The rotatably mounted shafts 2! within the: polishing heads I9 and 2'13 are then rotatedwhereby the eccentrically mounted pins 22 cause; the chucks I? and IS with which they engage: to oscillate the lens retained thereby over the polishing laps. I3 and Id with a circular polish ing motion. The sweep of this polishing circle is small, the radius being equal to the amount of. oifset of the pins 22 from the centre of the shafts 2I.

The base curve and cross curve surfaces. of

the cylindrical lens retained in the chuck of course substantially coincide with the'base and cross curve surfaces of the lap as stated above. These curves are retained in alignment with each other by means of the downwardly depending fingers 23 on the axis brackets 24. It perhaps should be mentioned that the fingers 23 are free to pivot in a plane at right angles to the longitudinal axis of the aligned bars Ila and III) which extend from the chuck in parallel spaced apart relation to the axis of a cylindrical sui face of a lens held therein and which slidably pass therebetween. During operation the lap holder II rocks in an arc beneath the lens to cause the polishing surfaces of the lap to move thereacross as the shaft, by which the lap holder is carried, rocks.

Reference will now be made to the arrangement and mounting of the lap holders I I and I2 on the rockably mounted shafts. The machine described is a double machine, that is, it is designed to polish two lenses at one time. Either or both of the two lenses can have positive or negative curvatures. To this end, the machine hasfour shafts, 28, 29, 30 and SI (Fig. 3), rotatably mounted in suitable bearings 32 and 33 (Fig. 27' within the casing II The bearings 32 and 33 for each shaft are similar. As will be seen from an examination of Figures 2 and 3, these shafts are arranged in a pair 28 and 29 and a pair 38 and 3|,

the shafts in each pair being disposed in vertical alignment with each other. V The free ends 34 of each of the four shafts project from the casing If! and carry a head 35 bevelled as at 3511 to receive a lap holder II or I2 in a locked dove-tail engagement. The free ends of the upper shafts 28 and 36 are each designed toreceive a lap holder II which depends downwardly therefrom to support a lap substantially as shown in Figure 6 while the lower shafts 29 and 3| are each designed to support a lap holder I2 which extends upwardly therefrom to support a lap substantially as shown in Figure 7.

The male dovetail section on heads 35 is designed to receive a female dovetail section on lap holders II and I2 in locked engagement from the top, and to this end the sides thereof flare out wardly from the top towards the bottom as at 35a to effect a wedge like union.

As n icated above, the lap holders u and I2 55 are caused-t ro'c'kin opieration to move the laps l3 and 14across a lens retained within'e'ach-of the chucks ll and I8.

Reference willnow'be made-to. thedrive mechanism for effecting thi rocking operation. :Rotational "power is supplied through a belt (not shown) to'a drive'pulley 3'! on the shaft-38 which rotatably mounted within thev casing 'l-i'i as at 38a and 3812. Also rotatably mounted within the casing l0 transversely of the shaft 38 is a shaft 39 which rigidly carries'a gear 46. The :gear 41! meshes with, and is driven bya worm gear 4| rigidly carried'by the's-haft38. The shafts 28 to 31 are rocked from the rotatable shaftdfithrough the crank links 42, 43, "44and 45 reciprocating rod 46 "and tie links 41, 48 and '49. Crank link '43 rigidly connects with journalled shaft 29 and pivotally connects with a free endofdrive rod-46 through stub shaft 43a. Drive rod 46 in turn is pivotally connected at its other free end to the rotating shaft'39 eccentrically of its longitudinal axis of rotation through stub shaft 85. It will be apparent that as the shaft 3-9 rotates-thewcentric connection thereof with the rod '45 will cause the latter to reciprocate and the-shaft 29 to rock through the crank link 43. The tie link 41 pivotally connects with the free ends of crank links 43 and 44 through stub shafts 43a and 44a. The link 48 pivotally connects with the freeends of the crank links 44 and 42 through stub shafts 44a and 42a respectively and tie link 49 'pivotally connects with cranklinks 42 and '45 through stub shafts 42a and 45a respectively. Cranklinks 42 and 45 are all-rigidly connected to their respective rocker shafts and similar in length sothat it will be apparent that the rocking motion transmitted to-link 43 by the reciprocating shaft 45 will be transferred to the remaining crank links by means of the above-mentioned tie links. The tie links 4'! and 49 are shownipartly broken away in Figure 3 to moreclearly show the-construction of the unit as a whole and the tie link 48 is broken away for similar reasons in Figure 2.

It will be apparent that the degree of rocking of the shafts 28 to 3| inclusive will depend on the eccentricity of the pivotal connection of the drive rod 46 with respect to the longitudinal axis of the rotatably mounted shaft 39 and-I have 'provide'd'a means for varying this eccentricity. Fig. 3b is an enlarged side view illustrating the means that I employ. It comprises a block 8| bored as at 82 and 83 to receive stub shaft 84 and a free end of shaft 39 respectively. Stub shaft 84 extends from one side of plate 85 and stub shaft 86 extends from the opposite side thereof with it longitudinal axis in parallel spaced apart relation to the longitudinal axis of stub shaft 84. Shaft 39 is keyed to the block 8| as at 39a, and stub shaft 84 is rigidly connected to block 8| by means of a threaded bolt 81 which passes through slot 88 in block 8| to threadedly engage with the stub shaft 84 as at 89. A washer 81a sits on the shoulders formed in the block ill by the slot '88. To lock the stub shaft 84 with respect to the block 8| the bolt 81 is tightened within the stub shaft 84. To adjust the eccentricity of stub shaft 86 with respect to stub shaft 85 it is 'merelynecessary to loosen bolt 87 and turn it within the slot 88. Slot 88 extends at right angles to the longitudinal axis of stub shaft 84 and it will be apparent that as bolt 81 is moved thereacross that stub shaft 84 will be caused to rotate within its bore '82. As stub shaft 84 rotates in its bore stub shaft-'86 will of course move 'relatively'to shaft '39. Stub shaft 86, it will be recalled. pivotally connects with a driven within the yoke 54 or 55.

V freeend of drive :rod. 46. The shaft 85 can he looked in anydesired relative position toshaftz 319: by tightening bolt-81 to secure stub shaft 84 rela tive to block;8 I

As stated-above the machine shown-is :adouble machine and the rocking shafts Hand 30 areal:- ranged in pairs. With each pair of shafts, is possible to polish'either aplus'ora minus lens, If it is desired to polish a plus lens, a lap holder f the type I2 is attached to the dovetail fitting 35 on the projecting free end 34 of the lower shaft of a pair to supportsa lap beneath the polishing heads l9. and 20. As will be apparent from the drawings, the upper surface of a lap. held in such a lap holder which extends upwardly from the shaft to which it is connected would describe a plus curve as it rocked back and forth while the upper surface of a lap held in a lap holder of the type H which extends downwardly from, the shaft to which it is connected would describe a minus curve as it rocks.

In use'one curve, usually the base curve, of the polishing lap is aligned in thelap holder, and the extent to which the lap holders extend from the shaft to which they are connected is predetermined, such that the base curve surface of the lens substantially coincides with the locus traced out by the said surface as the-shaft rocks.

Reference will now be made to the polishing heads l9 and 20 which oscillate lens holding chucks l1 and I8 respectively with a polishing motion above the polishing surfaces of'the laps I3 and I4 respectively. As will be'seen best in Figure 1 the twin heads l9 and 20 are rigidly connected to eachother'andare pivotally mounted as a unit between pins 25a and 25b in arms 25 and 26 as at 50, (Fig. 2). The heads are held together in the embodimentshown by means of the bolts 5| which pass through aligned holes bored in the flanges 52 and 53 on the yokes 54 and 55 of the heads [9 and 20 respectively.

Figure 5 is a sectional view of one of the polishing heads I9 and 20 showing the manner in which the rotatable shaft is mounted and The shaft 2| is exteriorly splined as at 56 to mate with the interiorly splined tubular shaft 51 which is in turn rotatably mounted within bearings in the yoke 54 as at 58 and 59.

The pin 22 is eccentrically mounted with respect to the shaft 2! by means of plugs 60 and 6|. Plug 60 engages in and is rigidly secured to the lower end of the shaft 2! by means of a pin as at 62. Plug 6| engages in a bore formed in the lower end of plug 60 eccentrically of the l0ngitudinal axis'of the shaft 2| and is retained therein by the cap screw 63. Pin 22 in turn engages in a bore formed in plug 6i eccentrically of its longitudinal axis and is retained therein by set screw 64.

Numeral indicates a cover plate which threadedly engages with the interiorly splined shaft 51 and is retained thereon by means of set screw 66.

'At its upper end the splined shaft 2| carries a thrust bearin housing 61 which is rigidly connected thereto by means of the set screw 68. Numeral 69 indicates a cover for the housing 67 which is centrally bored topermit the sleeve 10 to pass'therethrough. The sleeve H1 is formed with a flange H at its lower end to engage with a thrust bearing 72. At the upper end the sleeve 10 engages in a suitable bore in the head 13 and is rigidly held therein by a set screw 14,

A'guide-rod 15 extends upwardly from asuitable bore within the plug 60, through the hollow splined shaft 56, through the housing 61 and terminates in the sleeve 10. A compression spring I6 extends around the rod I5 between the top of plug 60 and a suitable thrust bearing TI which in turn bears against the lower end of sleeve 1 I.

I-Iead I3 is bored to slide vertically on a post 18 which extends upwardly from the yoke 54 and is provided with a hand screw 13a for the purpose of locking it in any position thereon.

Numeral I9 indicates a pulley which is rigidly mounted on the exteriorly splined shaft 51 by means of the set screw 80. In the operation of the polisher which was generally outlined above, the pin 22 engages with a suitable hole bored in the lens chuck holder, which in turn rests against the lap. Polishing pressure is applied on thelap by sliding the head I3 and the rigidly connected sleeve 10 downwardly on the post 18 to compress the spring I6. The vertical splines on the shafts 56 and 5? permit shaft 2| to move vertically with respect to the shaft 57!. Hand screw 13a can be tightened against the post I8 to retain the head I3 in any desired position. The shaft 2| is belt driven through pulley I9 and the shaft 51 (to which it is keyed by the vertical splines). Figure 5a is .a sectional view of .the matin splined shafts 2i and 51.

Detailed reference will now be made to the means employed for rocking the oscillating polishing heads I9, and 20. As indicated above, this rocking means includes the reciprocating shaft 21 which rigidly grips the transverse rod 02 which in turn is rotatably mounted in pins mounted in the upwardly extending arms 93 and 94, as at 95. The opposite end of the drive rod 21 is pivotally connected to the rotatably mounted shaft 96 eccentricall of its longitudinal axis whereby the drive rod 21 is caused to reciprocate as the shaft 96 is rotated.

The drive means for shaft 95 includes a mitre gear 9'! carried by the shaft as and adapted to operatively engage with the vertical shaft 98. Vertical shaft 98 in turn carries a gear 99 adjacent its upper end which operatively engages with the gear I carried by shaft 96. It will be apparent that as the shaft 38 is rotated, shaft 96 will also be caused to rotate through mitre gear 91, shaft 98, gear 93 and gear I00.

I also provide means for adjusting the eccentricity of the pivotal connection between the end of the drive shaft 21 and the shaft 98. This adjusting means comprises a stub shaft I0! ex tending eccentrically of the longitudinal axis of shaft 96 from a shoulder I02. A sleeve I03, bored eccentrically of its outer surface, fits over the stub shaft I01 and is recessed to cooperate with the shoulder I02.

A bearing I05, the inner race of which I00 fits over the eccentrically bored sleeve I03, and the outer race Ia of which is engaged by a free end of the drive rod 27, abuts against a shoulder I08 formed at the inner end of the sleeve I03. A plate I 09 is bolted to the stub shaft IIlI by means of the bolts I04 and Iilda and is designed to overlie an annular ring H0 which is keyed to sleeve I03 as at IIIJa. As the bolt I04 is tightened, its head exerts pressure against the outer end of the eccentrically bored sleeve I03 and ring IIO to force them against the shoulder I02 and inner bearing races I05 respectively to lock them rigidly with respect to the stub shaft IBI. The bearing I05 permits relative rotation of sleeve IGI within the end of rod 21, as the shaft rotates.

To vary the eccentricity of the end of the shaft 21 with respect to the longitudinal axis 'of the shaft 96, it is merely necessary to rotate the eccentrically bored sleeve I03 relative to the stub, shaft IN. This is effected by loosening the bolt I04 which releases the pressure of the sleevev I03 against the shoulder I 02 and permits relative rotation between the sleeve and the stub shaft. The ring H0 has a plurality of spaced apart radial bores in its periphery designed to admit a rod or key for the purpose of adjusting the sleeve I03 with respect to the stub shaft I0 I. It is possible to calibrate the ring I I0 and provide a pointer on the plate I09 to indicate the amount of eccentricity. After adjustment has been effected bolt I04 is of course re-tightened.

Figures 1 and 2 show the general construction of the housing for the shaft 95. It is not thought that too detailed a reference is necessary in this connection because any suitable housing would be satisfactory and the choice of a suitable hous' ing would merely require mechanical skill. In the embodiment shown, however, the housing comprises a vertically extending tubular post I II which is bolted to the main portion of the casing as at II 2 and carries suitable bearings H3 and II (Figure 4) designed to journal the shaft 96.

The detailed specification of all the component parts of the invention have now been outlined and it is now proposed to reconsider the operation of this device as a whole in fuller details than was considered at the beginning of this application.

In operation, a lap I3 or I4 is clamped into the lap holders by tightening the bolt H5 against shoulder H6 of the lap holder to cause the surface I I8 of the pivotally mounted block IIBa to rigidly retain the lap against the shoulder H9 formed at the rear of the lap holder. The lap, of course, is aligned such that its base curve will coincide with the locus of the surface defined thereby as the lap holder swings. As indicated above, the extent to which the lap holder extends downwardly or upwardl as the case may be, from the rockable shaft to which it is mounted, is predetermined to obtain this condition. The distance, of course, would be approximately equal to the radius of curvature of the base curve while deviations do not effect the result in practice.

The lens is then placed in the chuck I1 and I8 with its base curve aligned with the aligned arms. The aligned arms extend between the downwardly depending fingers 23 which are designed to retain the surfaces of the base curve of the lens and the lap aligned with each other. The top of the lens chuck is bored to receive the eccentrically mounted pin 22 of the rotatably mounted shaft 2|. A downward spring pressure is exerted on the lap holder by sliding the head I3 downwardly on the post I8 and tightening the key 13a against the post. As the lap holders rock during operation, the splined shaft 2I is rotated (within the vertically splined member 51) against the pressure of coil spring 16.

In this latter connection rotational power is transmitted to the shaft 2I through splined member 51 and pulley I9 which is in turn driven by the V belt I20 from pulley I2I adjacent the free end of shaft 38.

As stated above, the rotating shafts 2| move the lens in the lapholders with a reciprocating motion over the laps while the rod 21 reciprocates the polishing motion heads to a slight degree to vary the centre about which the polishing motion is effected.

From the above it will be apparent that I have disclosed a cylinder lens lapping machine that fully accomplishes the object of the invention. Lap holders are quickly and easily mounted on the projecting ends of rockably mounted shafts. The shafts are rotatably mounted in rugged bearings within the suitable frame and are arranged in pairs so that the machine can be quickly changed over to polish a plus or a minus lens. The construction of the machine readily lends itself to a multiple design which is capable of lapping several lenses at one time. This, of course, is effected by means of the tie links in the shaft rocking means.

Embodiments of the invention other than the ones shown and described in the specification will, of course, be apparent to those skilled in the art. I do not intend, therefore, that the scope of the invention should be limited by the foregoing except for the limitations expressed in the following claim.

What I claim as my invention is:

In a lens polishing machine, a frame, a shaft mounted in said frame for rocking movement about its longitudinal axis, a lap holder, the free end of said shaft being formed and said lap holder being formed such that said lap holder can be detachably mounted on said shaft, said lap holder being adapted to support a polishing lap in spaced apart relation from said "shaft and above said shaft whereby to cause the locus traced out by the surface of said lap as it rocks to coincide with the curvature of said lap, a second shaft mounted for rocking movement about its longitudinal axis and with its longitudinal axis in parallel spaced apart relation to said first shaft and above said first shaft, a second lap holder, a free end of said second shaft being formed and said second lap holder being formed such that said second lap holder can be detachably mounted on said second shaft, said second lap holder being designed to support av polishing lap in spaced relation from said shaft below said second shaft whereby to cause the locus traced out by the surface of said lap as it rocks to coincide with the curvature of said lap, a head mounted in said frame for rocking movement in the same plane as the longitudinal axes of said two shafts, a shaft rotatably mounted within said head and having a pin extending therefrom with its longitudinal axis offset from the longitudinal axis thereof, said in being designed for operative engagement with a lens chuck for a cylinder lens, and drive means for rocking each of said two shafts for rocking said head and for rotating said pin, saidhead having guide means for co-operation with the aforementioned lens chuck to keep the principal axes of thecylinder surfaces of the base and cross curves of a lens in alignment with the base and cross curves of the aforementioned polishing lap. f.

ALBERT BUTLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 761,061 Collinson May .31, 1904 1,199,519 Arnold Sept. 26, 1916 1,520,662 Maynard Dec. 23, 1924 1,827,748 Holman Oct. 20, 1931 2,020,312 Holman Nov. 12, 1935 2,381,449 Holman Aug. 7, 1945 FOREIGN PATENTS Number Country Date 241,312 Great Britain July 26, 1924 

